As glaciers move down valleys, they cause erosion. Pieces of rock embedded in the bottom of glaciers are dragged along the valley floor, resulting in abrasion. Where glaciers have retreated, we can see evidence of this erosional processes in small-scale features left behind. In this clip from the foreland of Nigardsbreen in Norway, geography researcher Dr Richard Waller shows us some excellent examples of striations and chattermarks associated with "rigid bed" glaciers.